The present invention relates to improvements in apparatus for transferring or conveying flowable materials from a first vessel (e.g., a stationary silo) into a second vessel (e.g., a mobile container which is mounted on an automotive vehicle or on a railroad car). More particularly, the invention relates to improvements in apparatus for transferring flour, concrete, gravel, sand or other flowable pulverulent and/or granular materials from a first vessel into a second vessel by establishing a path for gravitational flow of material from the first vessel into the second vessel.
It is already known to transfer flowable materials from a silo into a vessel therebelow by utilizing an apparatus which comprises a deformable upright duct whose median section constitutes a bellows and whose lower section is surrounded by a funnel. The lower section and the funnel are movable up and down so that the duct can be lifted above a vessel which is in the process of moving below or in the process of moving away from a position of register with the outlet of the silo, and that the funnel can descend into the opening of an empty vessel which has been placed into a position of register with the silo. The funnel defines with the lower section a compartment for evacuation of air which is expelled from the vessel during admission of flowable material. The means for moving the lower section of the duct and the funnel up or down comprises a winch. Air which is expelled from the vessel into the aforementioned compartment is evacuated by way of a pipe which is attached to the cover of the funnel. It is often necessary to connect the pipe to a suction generating device which promotes the outflow of air at the rate which is necessary to insure that large quantities of flowable material can enter the vessel per unit of time. The connection between the pipe and the suction generating device is flexible in order to allow for up-and-down movements of the funnel with the lower section of the duct. Suction generating devices are normally used when the flowable material is a pulverulent substance. Flexible connections between the suction generating device and the pipe on the cover of the funnel are relatively weak and are likely to be damaged or destroyed. At any rate, such connections are the (or one of the) most sensitive components of the apparatus.
In order to avoid the use of a flexible connection between the suction generating device and the apparatus of the above outlined character, certain apparatus are equipped with a second bellows which surrounds the bellows of the duct and is fixedly secured to the funnel at its lower end and to the upper section of the duct at its upper end. The space between the two bellows constitutes an extension of the aforementioned compartment and communicates with a pipe which is mounted on or carried by the upper section of the duct, i.e., which need not move up or down. This renders it possible to provide a rigid and hence more reliable connection between the suction generating device and the apparatus. As a rule, one can employ a larger and more effective suction generating device if the connection between such device and the apparatus is rigid.
The just discussed modified apparatus is more expensive than the apparatus without a second bellows. Therefore, apparatus with a single bellows will be used whenever possible, i.e., when one can operate without a suction generating device or when the provision of a relatively small suction generating device, with a flexible connection between such device and the apparatus, suffices to insure adequate evacuation of air during flow of material from the silo into the vessel therebelow. However, it happens again and again that the purchaser of an apparatus with a single bellows realizes the need for apparatus with two bellows or vice versa. This involves substantial expenditures including the purchase of a new apparatus or costly and complex conversion of apparatus with one bellows into an apparatus with two bellows. Furthermore, the manufacturer of such apparatus must maintain supplies of discrete parts for each of the two apparatus.